Gauges, such as fluid pressure gauges, have innumerable uses in industry. Price competition between the various gauge manufacturers is quite fierce. Therefore, a savings in the cost of material, labor and the like by a manufacturer can have a significant effect on that manufacturer's sales and profits. Therefore, a constant need exists among these manufacturers to develop more cost effective gauge manufacturing techniques.
The actual operating elements of the gauge are usually supported in a support structure. One of the most common support structures is a cylindrical case which supports the gauge within the case. A ring is mounted at one end of the case for supporting a transparent glass or window so that the gauge indicator can be seen. Two case types are commonly used. One type is called an open front case where the ring covers an opening in the case of essentially the same diameter as the case itself. The other type is a solid front case where the ring covers an opening in the case essentially just large enough to allow the indicator shaft to pass through without obstruction.
There are also two common types of rings used. The first type is known as a bayonet ring. The bayonet ring and case on which it is mounted have cooperating cam structures which secure the ring on the case by twisting the ring slightly relative to the case. The second type of ring is the sliding friction fit ring, which employs either a plastic member or an annular elastic member to frictionally engage the case.
To satisfy customer requirements, the typical gauge manufacturer has been required to maintain an inventory of four different cases, an open front case for receiving a friction fit ring, an open front case for receiving a bayonet ring, a solid front case for receiving a friction fit ring and a solid front gauge for receiving a bayonet ring. This inventory requirement is inefficient and costly.